when to start watering and how...

[napoleonbonaparte]

I got these pings as a gift and they are my first mexicans so I was wondering how to water mex pings (overhead or tray- I read both, but what is better?) and should I start watering them.
Here's how they look like:
I think this one should be watered- http://img340.imageshack.us/my.php?image=picture038hw7.jpg
I think this one is starting to grow it's summer foliage so also should be watered- http://img96.imageshack.us/my.php?image=picture040qh4.jpg
This one is still in winter growth and should be kept dry- http://img213.imageshack.us/my.php?image=picture041vz1.jpg
Is this right?

 

[DerbyCityNeps]

my P. x 'Titan' was still watered while in the winter growth. it never rotted. and same with my P. moranensis and jaumavensis. so i guess this rule of winter-dry, summer-wet isnt necessary. there are a few pings(not any of yours) that MUST have dry conditions in winter growth. and im sure Joseph is going to chime in and say somthing to prove me wrong good luck! that middle ping is a beauty with the red in the middle and green on the edges
Alex

 

[napoleonbonaparte]

But HOW damp must the soil be? Just slightly damp or wet like with other CPs?

 

[jimscott]

I would water now and wait until the "open tray" is almost dry.